1. Field of the Invention
The present invention relates generally to the fields of biochemistry and the stability and storage of biological samples. More specifically, the present invention relates to preservation of biological samples.
2. Description of the Related Art
Liquid biological samples may be utilized to test patients for a variety of medical conditions or measure in research subjects a variety of experimental variables in a non-invasive or minimally-invasive manner. Therefore, methods, apparatus and preservatives for collecting and storing liquid biological samples have widespread application in clinical and laboratory settings.
An example of a biological sampling method for saliva is disclosed in U.S. Pat. No. 4,774,962. A resilient absorbent inert body is chewed by a person and is subsequently introduced into a centrifuge tubule provided with an apertured floor. The centrifuged tubule is introduced into a centrifuge and subjected to a spinning process, whereupon the saliva is pressed out of the resilient body and passes through the floor into the lower part of the centrifuged tubule.
Another method and apparatus for collecting saliva from a test subject is disclosed in U.S. Pat. No. 4,580,577. A flavored absorbent mass, such as a sponge, for mastication, is chewed by the subject charging the mass with saliva. The saliva is subsequently expressed from the mass. An apparatus for this method includes a barrel-piston arrangement in association with a specimen vial for storage until diagnostic testing.
Another sampling device disclosing a piston for compressing a porous mass containing saliva is U.S. Pat. No. 5,393,496. The sample container is inserted into the collection container and becomes fluidly coupled thereto by inserting the saliva collector into the sample container and pressing therein. This allows a sample of saliva to be collected, separated from the saliva collector and retained within the collection container for testing. The saliva collector includes a piston fitting closely within the sample container and a porous mass which may be compressed by the piston in the sample container to extract the sample of saliva for distribution to the collection container. A buffering solution may be retained within the sample container for mixing with the sample of saliva.
U.S. Pat. No. 5,376,337 discloses a saliva testing device including a sample container opened at one end, a tube, a piston, a holding reservoir and a filter. The piston is fixed to a first end of the tube on a first side of the piston and has a hole in fluid communication with the tube. The piston fits closely and slidably within the sample container. An absorbent pad is affixed to the piston on a second side thereof in fluid communication with the hole in the piston. The holding reservoir is in fluid communication with a second end of the tube. The filter is in fluid communication with a second end of the tube. The absorbent pad receives a sample of fluid to be tested. When the piston is slidably inserted into the sample container, a pressure is generated forcing the saliva of fluid into the holding reservoir through the tube.
U.S. Pat. No. 5,380,492 discloses a saliva sampling device including a sample container, a cap, a sample collector and a sample adequacy system. The sample container has an inner wall surface and a retaining ridge which is disposed on the inner wall surface. The sample collector includes a piece of filter paper and a holder which has a tube and a paddle coupled to the piece of filter paper. The paddle has a peripheral edge for engaging the retaining ridge of the sample container. The cap has an outer wall surface and an inner wall surface. The outer surface snugly engages the inner wall surface of the sample container. The inner wall surface has a truncated conical portion having a top and a cylindrical portion which is coupled to the truncated conical portion adjacent to the top thereof The truncated conical portion thereof slidably engages the tube in order to guide the tube so that the cylindrical portion thereof snugly engages the tube.
U.S. Pat. No. 4,938,963 to Parnell teaches the use of citric acid and sodium benzoate to stimulate saliva production and to facilitate the use of the Yerba Santa fluid extract of the lozenge, respectively. U.S. Pat. No. 5,022,409 to Goldstein teaches an oral rinse for the collection of immunoglobulins and other substances from saliva and U.S. Pat. No. 5,103,836 to Goldstein teaches a kit and apparatus for the collection of saliva samples. However, in both of these patents of Goldstein, citric acid is used exclusively as a saliva production stimulator. Furthermore, the presence of sodium benzoate is meaningless because each device is adjusted to a final pH of 6.5 and as is well known in this art, sodium benzoate is not effective as a preservative at pH values above 4.0.
The prior art is deficient in the lack of effective means of preserving a biological sample containing analytes, e.g., proteins, lipids and carbohydrates. The present invention fulfills this longstanding need and desire in the art.